As an image display device (also referred to as “display device”) such as a television receiver, and a monitor of personal computer, for example, a cathode ray tube (CRT) display device, a liquid crystal display device (LCD), a plasma display device (PDP), an electroluminescent (EL) display device and the like are known. Of these display devices, a plasma display device to which attention is paid in the field of a large-screen display device utilize plasma discharge for light emission, and thus, there is a concern that unnecessary electromagnetic waves of a band of from 30 MHz to 1 GHz leak out to exert an influence upon other instruments (for example, a remote control instrument, an information processing device, etc.) For that reason, it is general to provide an electromagnetic wave shielding material in a film form for the purpose of shielding the leaked electromagnetic waves on the front side (observer side) of a plasma display panel which is used in a plasma display device. In an electromagnetic wave shielding material which is set up on the front (screen) of an image display device of this kind, a conductive layer thereof is formed in a pattern shape such as a mesh, for the purposes of transmitting visible light therethrough and shielding electromagnetic waves.
The “electromagnetic waves” as referred to in the specification of the present application mean electromagnetic waves (radio waves) of a band of from kHz to GHz among electromagnetic waves in a broad sense, and among electromagnetic waves in a broad sense, infrared rays, visible light and electromagnetic waves of an ultraviolet band are to be called “infrared rays”, “visible light” and “ultraviolet rays”, respectively.
Though various investigations have hitherto been made regarding such an electromagnetic wave shielding material, in recent years, in view of advantages of low cost and high productivity, attention is paid to a specification in which a conductive composition (also called “conductive ink”, “conductive paste” or the like) is printed in a prescribed pattern. In a conductive composition of this kind, since conductive particles are dispersed in an electrically insulating resin binder, there is involved such a problem of how to reduce the electrical resistance (to increase a conductivity) of the conductive composition. In order to solve such a problem, for example, Patent Document 1 proposes a method for manufacturing an electromagnetic wave shielding material by subjecting a conductive composition containing conductive particles, a binder and a solvent to screen printing in a geometric pattern on the surface of a transparent porous layer of a transparent resin substrate which is provided with the transparent porous layer containing an oxide ceramic, etc. as a main component and then subjecting the printed transparent resin substrate to a heat treatment to form a conductive part of the geometric pattern, and an electromagnetic wave shielding material.
Also, Patent Document 2 proposes an electromagnetic wave shielding film prepared by forming a geometric pattern containing metal fine particles on a transparent support and subjecting the formed geometric pattern to a heat treatment, thereby regulating a surface resistivity of the geometric pattern to not more than 106Ω/□.
On the other hand, as an electromagnetic wave shielding material composed of a pattern layer having a metal layer formed by means of plating, Patent Document 3 proposes an electromagnetic wave shielding material prepared by subjecting an electroless plating catalyst paste to screen printing in a mesh pattern on a transparent substrate and forming a metal layer thereon by means of electroless plating. Also, Patent Document 2 proposes an electromagnetic wave shielding material prepared by subjecting a conductive composition to intaglio offset printing in a mesh pattern on a transfer material, transferring the mesh pattern on the transfer material onto a transparent substrate and electroplating a metal layer on the mesh pattern on the transparent substrate. Also, Patent Document 5 proposes an electromagnetic wave shielding material prepared by subjecting a conductive composition to intaglio printing in a mesh pattern directly on a transparent substrate and forming a metal layer on the mesh pattern on the transparent substrate by means of electroplating. Furthermore, Patent Document 6 proposes a method for manufacturing a conductive base having a metal fine particle layer in a mesh form laminated on at least one surface of a base, wherein the metal fine particle layer is treated with an acid.    [Patent Document 1] WO 2006/129568    [Patent Document 2] JP-A-2008-66574    [Patent Document 3] JP-A-11-170420    [Patent Document 4] JP-A-2001-102792    [Patent Document 5] JP-A-11-174174    [Patent Document 6] JP-A-2006-313891    [Patent Document 7] WO 2008/149969